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"The clutch on the compressor definitely engages".
Ok, one down two to go.
"Would a prolonged leak check help to pinpoint the problem areas and which hoses needed to be replaced?"
No. Rather a prelonged "vacuum" would insure moisture and stray gases are removed. When you leak down test for gross leaks, meaning you pull a vacuum, lock up your service set valves and watch the low side gauge, you are simply checking for a "gross" leak... a leak that would be obvious if you were to inject refrigerant later.
The typical procedure for finding leaks is:
1) Pull your vacuum on the system.
2) Inject tracer dye with the refirgerant oil.
3) Charge the system with refrigerant.
4) Use an electronic leak detector to check all major components and hose fittings. If you find a leak you fix them, if you don't find a leak (which is common with the typical stock old hose scenario) you
drive the car with the ac on for few days or hours.
5) Then you use an a/c UV black light to check all the major components and fittings for signs of tracer dye. If you don't find any telltale signs of tracer dye (which is common with the typical stock old hose scenario) you decide whether you want to take the smart step and replace all the hoses.
The hose issue (you can find posts here, on other websites, etc.) is as follows:
The a/c hoses used prior to the introduction of R134a where non-barrier (aka common ac hose developed 40 years ago). A "barrier" hose has an additional liner inside which greatly reduces the rate of permeation (leakage). When the common ac hose was developed it was in cars with front mounted engines and front mounted single condensers which typically required less than 10 feet of non-barrier hose. During that time period R12/ozone concerns and cost per pound were not an issue. The 911 is not layed like a front engine car, it has nearly 40 feet of non-barrier hose. Non-barrier hose leaks xx parts per million per linear feet at xx degrees and xxx pressure. Over time the refrigerant simply leaks out of the non-barrier hose more quickly than barrier hose.
Electronic refrigerant sniffers and UV tracer dyes are not sensitive enough to detect the slow leaks through non-barrier hoses.
Replace the hoses and most of your problems will go away. If you have not replaced your drier then you do that at the same time. Since you are removing alot of volume (40 feet of hoses) you might at well add additional refrigerant oil prior to recharging the system since the oil is displaced through out it.
And while you are replacing the hoses remove your evaporator, clean or replace it, properly re-seal the unit and the evap box.
Then drive in a more comfortable car more often and move onto the next challenge.
PM if you need more help.
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